Process and apparatus for dry milling of coal and its by-products



Aug. 7, 192s.

H. M. SUTTON ET A1.

y PROCESS AND APPARATUS FOR DRY MILLING OF COAL AND ITS BYTPHODUCTS Filed Aug. l5, 1923 Aug. 7, 1928. 1,679,922 H. M. sUTToN ET AL PROCESS AND APPARATUS FOR DRY'MILTIIING OF COAL AND ITS BWI-PRODUCTS Filed Aug. 15. 1925 5 Sheets-Sheet 2 C 01. 5 w p1 lo w s *if k 8 w L Il 1,679,922 ET AL 5 sheets-sheen 3 Aug. 7, 1928.

H. M. SUTTON.

PROCESS AND APPARATUS FOR DRY MILLING OF GOAL AND ITS BY PRODUCTS Filed Aug. l5, 1925 Aug. 7', 1928. 2 1,679,922

H. M. SUTTON ET AL PROCESS AND APPARATUS FOR DRY MILLING' OF COAL AND ITS BY" PRODUCTS Filed Aug. 15, 1923 5 Sheets-Sheet 4 Aug. 7, 1928.

H. M. SUTTON ET AL PROCESS AND APPARATUS FOR DRY MILLING OF COAL AND ITS BY-PRODUCTS Filed Aug. 15, 1923 5 sneets-shet 5 fk. m, @i Am,

hill

Patented Aung. 7, 1928.

UNITED- STATES .PATENT OFFICE.

HENRY MOORE SUTTON, WALTER LIVINGSTON STEELE, AND EDWIN GOODWIN STEELE,

. OF DALLAS, TEXAS.

PROCESS AND APPARATUS 'FOR DRY MILLING 0F COAL AND ITS 'BY-PRODUCTS.

Application led August 15, 1923. Serial No. 657,567.

rIhis invention relates to improvements in the process and apparatus for dry mllling of coal" and its byproducts, and it pertains to certain improvements whereby the. stream of coal entering the mill for separation and cleaning is automatically taken care'of by the, following construction, which carries out our process. s

We have discovereda process after a long period of experimentation that increases enormously the out-put of the mill, which process will now be described.

rllhe coal to be handled by our process and apparatus diii'ers widely in character, and it is necessary that it be milled or cleaned for different purposes. This wide variation oit the character and object of cleaning necessitates the design of milling plants to suit the conditions to be met as to capacity and out-put, as well as metallurgical requirements to suit the character of coal to be milled. Consequently, variations in the apparatus can be made without departing from the scope of our present invention, and the following disclosure illustrates these designs which are expressions of our invention.

In the accompanying drawings: p

Figure l illustrates an apparatus involving our process when all the coal is being sized and cleaned. I

Figure 2 is an expression of our apparatus which involves the additional step of separating the final undcrsize product by airsuction.

Figure 3 shows an apparatus which carries out our process when only a portion of the coal is cleaned, and the inal screen under-size product is passed directly to the cleaned coal product..

Fig. 4, is a'longitudinal vertical sectional view of one form of screens showing thev method of separating the different sized particles of the mass.

Fig. 5, is a top plan View feeder being omitted.v

Fig. 6 is a longitudinal Vertical sectional view oit another form of screens, showing the method of separating the different sized particles of the mass.

Fig. 7 is a top plan view of Fig. 6, the said feeder being omitted.

Referring now to Fig. l of the drawings,

of rig. i, uw`

which is a View showing the elements diagrammatically. In this view the coal to be separated and cleaned is supplied to the lower end of a vertically arranged elevator 1,` which elevates it and deposits itupon a4 `feeder 2. From the feeder it falls upon a vibrating screen 3, which separates 'the coal, a portion 'falling into the bin 4, located below it, theundersize coal Jfrom the screen 3 falls upon the screen 5, as shown by arrow views of the forms of screens that are de-l scribed hereinafter, and which are diagraminatically shown in the drawings. In` Fig. 4 the mass is fed upon the screen 3', the over-sized particles flowing over the screen and falling into the discharge spout 3, while the under-sized product falls through the screen 3 down upon the screen 5', Jfrom which the over-sized falls into the discharge spout 5, the under-sized product falling through the screen uponthe screen 8 from which it Hows into the discharge spout 8, and therk under-sized Howing through the screen 8 to thesucceeding' screen. It will be observed in this process that part of the under-sized from the screen 3 becomes the over-sized in the screen 5 and so on throughout the series of screens. The screens 3', 5. and 8 comprise dierent sized Ymesh, whereby the different result is accomplished, as is fully described hereinafter.

In Figs. 6 and 7, another form of screen is shown, which operates upon the same principle, as that described in` respect to Figs. 4 and 6, and it is unnecessary to repeat the description.'4

Below each bin is located a dry separating machine 13, which separates the products that fall'upon the separators from the bins. The coal fed from the bins to the separators is cleaned and separated into coal, middlings and waste. By dotted linges and arrows these several separations are shown as fed into conveyers 14, 15, and 16. The separated coal is the desired grade, while the mddlings are returned to the elevator 1, where they aga-in pass through the screens above the bins, through the bins and through the separators. The waste or refuse is disposed of by being fed through the conveyer 16 to a dump. By this means the middlings are subjected to re-separation. In referring to middlings, we mean a product which is cut between any other two products and is composed of the elements of both of such products. Hence the necessity for the reseparation to`prevent any waste and to obtain the full amount of coal from the mass being acted upon.

Fig. 2 operates exactly as disclosed in Fig. 1, and to which the same reference letters are applied as far as they are applicable. In this figure we have added an aspirator 17, to which the undersize screened product is fed, and this aspirator draws from the material fed to it the dust which is conveyed to a collector (not shown) whereas the remaining material falls through the aspirator 17 tov the bin. In this figure there are two grades of coal which are delivered from the separators 13 to the ccnveyers 18 and 19, the one 18 collecting coal No. 1, and 19 coal No. 2. The middlings conveyer 15 of this view conveys them to the elevator 1, Where they are returned for re-separation, while the refuse conveyer 16, conveys the waste to the refuse dump.

In Figs. 1 and 2 the direction of coal, middlings, and waste to their respective conveyers is shown by the dotted lines and arrows. For instance, in Figs. 1 and 2, the

flow of coal is indicated by dotted line `20,

middlings by 21 and waste by 22.

In Fig. 3 is shown an apparatus utilizing four bins, instead of five, as in the other figures, and this apparatus is used when only a. portion of the coal milled is cleaned or separated, the final undersize product pass- -ing directly to the cleaned coal product. The

same reference numerals are vused as far as they are applicable, as 'are used in Fig. 1.A

In this figure the dotted line 23 indicates the flow of the undersize to the coal conveyer 14. In other respects it is substantially the same as shown in Fig. 1, the separatorslS being of a different form. It will be understood that the exact type of separator does not affect our invention so long as it is a type that produces coal, middlings, and refuse.

The foregoing described apparatus comprises essentially the following fundamental principles:

` 1. Sizing coal for separation by removal of screen oversize products.

2; The use of conveying-screen umts to distribute the screen oversize ,products to the point of separation.

3. Equalizing orstorage bins between t-he sizing or screening operation and the cleaning or separating operation.

4. The production of middlings products and the automatic return of such middlings products for resizing and recleaning.

The ordinary screening or sizing of coal is done by removing the undersize screen product, or the use of stationary screen units which require the subsequent distribution of the screen products by means other than the screen unit itself.

We recommend the use of our patented sizing and separating units, such, for Ainstance, as the screening unit patented April 20th 1915, #1,136,293 and the separating unitspatented Dec. 20th 1910, #979,046 Sept. 23rd 1913, #1,073,644, Sept.. 91h 1919, #1,315,881, or a separator combining various elements of these inventions, although We do not confine the application of this process to any type of screen or separating unit except that in sizing coal for dry separation a screening unit must be used which discards its oversize product for subsequent separation and during the process of screening automatically conveys such oversize products to a point or position where it will be available for separation.

Referring to the drawings again,

Fig. 1 illustrates the process when all of the coal is sized and cleaned, the final screen operation producing both an oversize and undersize product and the undersize product being separated Without further sizing. This How-sheet shows a separation ot the sized coal into three products. viz: cleaned coal, middlings and refuse, the middlings being finally returned to the original uuseparated coal at the elevator 1, and mixed therewith, to be separated with the original unseparated coal.

Fig. 2 illustrates the process when all of the coal is sized and cleaned, the final step of sizing being done by separating the final screen undersize product to remove, by air suction, the dust or smaller particles of that product to produce a pneumatically sized oversizeproduct for separation. The flowsheet shows a separation of the coal into two coal products when more than one grade of coal is desired:

Fig. 3 illustrates the process when only a portion of the mill feed is cleaned, the final screen undersize product passing direct to the cleaned coal product.

Figs. 1 and 3 show the Sutton. Steele Sn Steele type ofscreening unit, Fig. 2 an ordinary tipple screen arranged to discard its oversize product at each step in the sizing operation. Figs. 1, 2 and 3 show the automatic return of the middlings products and resizing and recleanin Figs. 4, 5 and 6 sow definite sizes of screen apertures and handles ya definite screen schedule of prepared sizes of coal lll for separation. This was shown merely to better illustrate the removal from the sizing apparatus of the screen oversize product and the subsequent separation of that product. lt is understood that this process is not confined to any screening schedule or to any definite number of sized products for separation, these being governed in all cases by the character of the coal to be milled, the object of milling, the capacity, type of machine used and other factors which necessarily enter into the design of a milling plant for dry coal preparation.

lln the ordinary method of sizing c0al,`

When the undersize screen product. is first discarded and the oversize material is then further sized or screen separated, any breakage of the particles of the undersize screen product leaves these finer size particles in the product. Consequently if the product is handled in conveyors, or by other means, breakage occurs and an undersized product is delivered for separation. When this operation is reversed and the coal is separated into several sizes for separation by discarding the screen oversize product at each step in the screening operation any breakage which might occur during the operation of screening is automatically corrected by such liner size particles immediately passing to the screen undersize product and then to a screening surface with smaller l,size apertures, thus automatically placing such smaller particles With particles of similar size before discarding the same for separation as an oversize screen product.

To further` simplify the method of milling and to maintain the efiiciency of the above screening method this process contemplates the use of screening or sizing units Which, While sizing the coal into the necessary number of sized products for separation, automatically conveys its products to a point or position Where it will be available for separation Without the use of conveyors for such Work, thus avoiding the breakage resulting from such handling.

The advantages secured in placing bins between the screening and separating operations is explained by comparison with an operation which does not include this important feature. The stream of coal entering a cleaning mill differs in character from hour to hour and from day to day as the coal brought from the mine or shipping pointy differs. This difference means that the coal supply is not uniform in character or quantity. Without the bins the separators may be running empty at one period and be overloaded at another period or because of aA larger proportion of larger size particles, or the reverse, a portion of the equipment might be overloaded While the remaining portion of the equipment would be running empty or partially loaded, thus greatly interfering with the successful operation of the plant and increasing the diiiiculties of operation. When any unit of such a plant fails from any cause, or it is desired to stop a unit temporarily for any cause it is necessary to close down the entire plant. y n

Placing bins between the screening and separat-ing operations permits the operation of the sizing or separating equipment Without regard to the equipment not operated, and by placing a bin above each separating unit that unit may be operated or shut down without interfering With the operation of any `other unit of the equipment. The bins also act as equalizers to automatically maintain a constant flow of material to the separators regardless of variation in quantity of feed to the mill or of variation 1n the sizing characteristics of the coal handled as the storage capacity of such bins is sufficient to overcome inequalities of feed to the screening equipment. These bins also permit the operation of the 'sizing equipment While the separating equipment is at rest, or the reverse, as stated above, thus permitting the operation of the screens for, say, one shift during the day While the separating equipment may be operated for a longer period when desired.

lVe have found that a separator, of any type, used for separating dry materials is not efficient in its operation unless it is capable of producing a middling product or unless inthe operation a middling product is produced. Either the unit itself mustmake middlings or a middlings unit of the same character of machine must be used as a middlings purifier.

When a middlings product is cut from between. any two products this results in a further cleaning of the products being produced on each side of the product cut out, as it removes that portion of the material which might overlap during the separation and thus result in a mixed product. When no middlings are cut out and any two zones or separated material is divided at their junction it is impossible to so operate a machine as to maintain the zones constantly at any one point and impossible to so divide these zones as to prevent a certain amount of mixing at the dividing point. When middlings products are cut out the width` of the middling zone permits a certain variation in the shifting of the zones without altering the middlings adjustment and Without any mixing of the finished products.

To efficiently handle middlings products in milling coal it is necessary that this product be resized before it is returned for recleaning. Consequently our process contemplates returning this product to the head-end of the screening equipment (elevator 1) when it is automatically distributed with the original lUl) ' each step in lthe screening unseparated coal to the proper screening unit for resizing and is sent automatically to the proper separating unit for recleaning.

As previously stated, the character of coal differs to such an extent and the uses and ob'- 'ject of cleaning is so variable as to necessitatejthe design of milling plants to specifically meet conditions. The production of one grade of coal only may be sufiicient while two or more grades might be necessary. In sizing some coal the resulting sized product might be automatically cleaned of refuse in thev coarser size, while sizing other coals might automatically free the finer sizes of refuse, this being governed by the sizing characteristics of the coal. Then this occurs, it becomes unnecessary to further clean such products which are cleaned by screening and in Fig. 3, we show a How-sheet for a coal which does not require cleaning of the final screen undersize product, that product having been cleaned by screening the refuse into the coarser sizes. This variation in the sizing characteristics of coal is due to variation in the comparative hardness of the coal and refuse material. When sizing a coal which carries a refuse material which is harder than the coal the coarser sizes will carry the bulk of the refuse, the coal having been pulverized finer than the refuse in mining and subsequent handling and consequently when sized the finer sizes will run higher in carbon than the coarser sizes.

The reverse is true of a hard coal carrying a soft refuse material, when sizing produces dirty products in the liner sizes and comparatively clean products in the coarser sizes. This characteristic of coal sometimes makes 'further cleaning of screen products unnecessary when efiicient screening is done, that operation producing cleaned coal by screening, the screen products which are n`ot thus cleaned being cleaned by separating units as vshown on the drawings.

Summarizing the above, it will be noted that our process consists of first sizing the mill stream by discarding from the sizing apparatus the oversize screen product at operation, the use of screening units which distribute the oversize products to a point convenient for separation, the use of storage bins between the screening and separating operations to equalize the flow of material to the separators and to facilitate mill operation and the return of middlings products for resizing and recleaning.

It will be understood that the several apparatus will be arranged mechanically so that one or more of them may be stopped temporarily, which stopping, as above explained, does not affect the working of'the other units. Also the complete screen or sizing elements may be stopped while the separating elements are in operation or vice coal, middlings versa, thus permitting the process to be continuous.

This mechanism will be equipped with any desired mechanical means, whereby either screen, or either separator may be stopped without aiecting the other units, or the Whole screening or sizing stopped while the separators are operating without affecting the continuity ofthe result,'and vice versa.

The screening or sizing elements are constructed so that the oversize or larger elements are diverted laterally and flow into the bin, while the smaller elements flow through onto the succeeding screen. Such a screening construction is shown in our Patent No. 1,136,293. above mentioned.

Having thus described our invention, what we claim and desire to secure by Letters Patent is: l

1. A continuous process for dry separating the elements of a mass, which consists in sizing and separating the elements into clean, middlings. and refuse products and finally and directly returning said middlings first to said sizing and then to the separating step for the purpose described.

` 2. A continuous process for dry separating the elements of a mass, which consists in sizing and separating the elements into and refuse, and returning said middlings in the condition they were when discharged first directly to the originally unseparated elements for the purpose of subjecting them to sizing and the'n to separation.

3. A continuous process for dry separating the elements of a mass, which consists in sizing and separating the mass into coal, middlings, and refuse, then subjecting the said middlings in the condition they were when discharged directly first to the said sizing and then to the separating for the purpose specified.

4. A continuous process for dry separation of the elements of a mass, which consists in repeatedly sizing the mass, separating the middlings from said elements and mixing it with the mass before separation thereof, thereby subjecting the middlings to repeated sizing, storing the sized elements whereby the separating operates from the storage irrespective of the successive amounts sized and irrespective of the variation in operation of the repeated sizing.

n apparatus for sizing and -separating elements of a dry mass, comprising a pluralit-y of sizing screens, a plurality of separators, and a plurality of storage bins located respectively between the sizers and separators, the storage bins being of greater capacity than either of the sizing screens or the separators, whereby the separators may operate irrespective of the operation of the sizing screens.

6. An apparatus for the separation of elements ofa dry mass, comprising a plurality of sizing screens all arranged substantially in a horizontal line, a plurality of bins receiving the separated material from the sizers, a plurality of separators arranged to receive the material from the said bins, the bins having greater capacity than that of the screens or the separators whereby the bins supply the sized material to the separators irrespective of the output received by 1o our signatures.

IIENRY NIooRE sUTToN. wALTEE LIVINGSTON STEELE. EDWIN coonwIN STEELE. 

